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com.google.errorprone.bugpatterns.OperatorPrecedence Maven / Gradle / Ivy
/*
* Copyright 2016 The Error Prone Authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.errorprone.bugpatterns;
import static com.google.errorprone.BugPattern.SeverityLevel.WARNING;
import static com.google.errorprone.matchers.Description.NO_MATCH;
import static com.google.errorprone.util.ASTHelpers.getStartPosition;
import com.google.errorprone.BugPattern;
import com.google.errorprone.BugPattern.StandardTags;
import com.google.errorprone.VisitorState;
import com.google.errorprone.bugpatterns.BugChecker.BinaryTreeMatcher;
import com.google.errorprone.fixes.SuggestedFix;
import com.google.errorprone.matchers.Description;
import com.google.errorprone.util.ASTHelpers;
import com.sun.source.tree.BinaryTree;
import com.sun.source.tree.ParenthesizedTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.tools.javac.tree.JCTree.JCBinary;
import com.sun.tools.javac.tree.TreeInfo;
import java.util.EnumSet;
/** A {@link BugChecker}; see the associated {@link BugPattern} annotation for details. */
@BugPattern(
name = "OperatorPrecedence",
summary = "Use grouping parenthesis to make the operator precedence explicit",
severity = WARNING,
tags = StandardTags.STYLE)
public class OperatorPrecedence extends BugChecker implements BinaryTreeMatcher {
private static final EnumSet CONDITIONAL =
EnumSet.of(Kind.AND, Kind.OR, Kind.XOR, Kind.CONDITIONAL_AND, Kind.CONDITIONAL_OR);
private static final EnumSet SHIFT =
EnumSet.of(Kind.LEFT_SHIFT, Kind.RIGHT_SHIFT, Kind.UNSIGNED_RIGHT_SHIFT);
private static final EnumSet ARITHMETIC =
EnumSet.of(Kind.PLUS, Kind.MULTIPLY, Kind.DIVIDE, Kind.MINUS);
private static final EnumSet SAFE_ASSOCIATIVE_OPERATORS =
EnumSet.of(Kind.CONDITIONAL_AND, Kind.CONDITIONAL_OR, Kind.PLUS);
@Override
public Description matchBinary(BinaryTree tree, VisitorState state) {
Tree parent = state.getPath().getParentPath().getLeaf();
if (!(parent instanceof BinaryTree)) {
return NO_MATCH;
}
if (TreeInfo.opPrec(((JCBinary) tree).getTag())
== TreeInfo.opPrec(((JCBinary) parent).getTag())) {
return NO_MATCH;
}
if (!isConfusing(tree.getKind(), parent.getKind())) {
return NO_MATCH;
}
return createAppropriateFix(tree, state);
}
private static boolean isConfusing(Kind thisKind, Kind parentKind) {
if (CONDITIONAL.contains(thisKind) && CONDITIONAL.contains(parentKind)) {
return true;
}
return (SHIFT.contains(thisKind) && ARITHMETIC.contains(parentKind))
|| (SHIFT.contains(parentKind) && ARITHMETIC.contains(thisKind));
}
private Description createAppropriateFix(BinaryTree tree, VisitorState state) {
// If our expression is like: (A && B) && C, replace it with (A && B && C) instead of
// ((A && B) && C)
return SAFE_ASSOCIATIVE_OPERATORS.contains(tree.getKind())
&& tree.getLeftOperand() instanceof ParenthesizedTree
!= tree.getRightOperand() instanceof ParenthesizedTree
&& parenthesizedChildHasKind(tree, tree.getKind())
? leftOrRightFix(tree, state)
: basicFix(tree);
}
private Description leftOrRightFix(BinaryTree tree, VisitorState state) {
int startPos;
int endPos;
String prefix = "(";
String postfix = ")";
if (tree.getRightOperand() instanceof ParenthesizedTree) {
startPos = getStartPosition(tree.getRightOperand());
endPos = getStartPosition(tree.getRightOperand()) + 1;
postfix = "";
} else {
startPos = state.getEndPosition(tree.getLeftOperand()) - 1;
endPos = state.getEndPosition(tree.getLeftOperand());
prefix = "";
}
return describeMatch(
tree,
SuggestedFix.builder()
.prefixWith(tree, prefix)
.replace(startPos, endPos, "")
.postfixWith(tree, postfix)
.build());
}
private Description basicFix(BinaryTree tree) {
return describeMatch(
tree, SuggestedFix.builder().prefixWith(tree, "(").postfixWith(tree, ")").build());
}
private static boolean parenthesizedChildHasKind(BinaryTree tree, Kind kind) {
Kind childKind =
ASTHelpers.stripParentheses(
tree.getLeftOperand() instanceof ParenthesizedTree
? tree.getLeftOperand()
: tree.getRightOperand())
.getKind();
return childKind == kind;
}
}